The present invention relates to a stream data recording and playback apparatus for recording and playback of stream data such as digital video/audio signals and a method for transfer of data in the stream data recording and playback apparatus.
With the development of digital video signal processing techniques and recording and playback techniques, settop boxes (STB's) for reception of satellite broadcast or CATV, digital broadcast receiver sets such as digital TV's, digital VTR (Video Tape Decoder, or VCR (Video Casette Recorder))'s, disk recorders and the like have been realized as household apparatuses. When a video/audio signal is transmitted and received between the digital AV apparatuses, it is desirable for the purpose of preventing degradation in signal quality that the signal be transmitted as stream data while keeping the digital signal format. Available as a digital interface optimized for transmission of such stream data is a fast serial bus defined by IEEE 1394-1995 standards, which bus will hereinafter be referred to as a 1394 bus. The 1394 bus meets conditions for connection of the AV apparatus by permitting maximal 63 devices to be connected freely in tree connection and by being provided with an isochronous transfer scheme that has a maximum transfer rate of 400 Mbps and is suitable for transmission of data necessary to be transmitted on real time such as a video/audio stream.
In the recording and playback apparatus such as a digital VTR (or VCR), on the other hand, recording/playback of signals is carried out digitally, so that a change in signal quality attributable to repetitive recording/playback operations does not occur essentially and copies identical to an original can be created easily many times. This will give rise to a possibility that many copies duplicate to an original can be reprinted, amounting up to a great number of copies in excess of the range of domestic use, even in the case of video/audio data (contents) conserved for copyright.
As a technique for prevention of the unauthorized copy of contents, a DTCP (Digital Transmission Contents Protection) scheme has been adopted in the 1394 bus. In the DTCP scheme, data for authentication is assigned to AV apparatuses, one by one, for handling a video/audio stream with copyright reserved, that is, a broadcast receiver set, a recording and playback apparatus and a display apparatus, a stream applied with a scramble process is sent from an apparatus on the stream transmitting side (hereinafter referred to as a source device) in order that transmission of data is permitted between only apparatuses that succeed in mutual authentication and an apparatus on the stream receiving side (hereinafter referred to as a sink device) that has acquired key data for release of the scramble in advance on the basis of the authentication receives and decodes the stream to play back or record the stream.
The video/audio stream is assigned with copy control information describing conditions for copying of data and data copying is sorted into any of three modes of “copy free”, “copy never” and “copy one generation”. The recordable apparatus such as the digital VTR is permitted to receive and record only a stream subject to “copy free” or “copy one generation” and after having recorded a stream subject to “copy one generation”, it changes the copy control information to “no more copies”. The apparatus for playback and display of video/audio signals such as the digital TV can receive and plays back streams regardless of the copy control information.
One may refer to, for example, JP-A-11-205310 as describing the aforementioned technique.
In the DTCP scheme, once contents subject to “copy one generation” is recorded on the recording and playback apparatus, copy control information for the contents is thereafter changed to “no more copies”, thus inhibiting other recording apparatus from recording the contents any more. On the other hand, a stream recording/playback apparatus for recording video/audio stream data by using a hard disc drive (HDD), such as a so-called HDD recorder”, has recently been realized. In the HDD recorder, the drive is fixed in the apparatus and the capacity is limited and therefore, from the standpoint of easy-to-handle operation, it is desirable that the user delete contents once played back and unnecessary to be conserved thereafter from the disk, keep contents desired to be played back later in the disk and with the empty capacity of the disk lessened, transfer the contents to be kept to a VTR or optical disc apparatus so that the contents may be stored in a holding medium such as a tape or optical disc.
In the copyright protection method described as above, contents once recorded in the recording medium is managed as “no more copies” and consequently, cannot be copied again to the holding medium, with the result that conservation by the user as described above cannot be realized.